Officially, it's a column-oriented database. This means that, internally, it stores columns together rather than rows together. In practice, it means that it's optimized for calculating analytics over large datasets.
I've found, from personal experience, that it makes a good replacement for time-series databases, even though it's technically not a time-series database. My employer migrated our KPIs and other metrics from InfluxDB to ClickHouse a couple of years ago, and the drastic improvements in performance were well worth the time it took to migrate our data. It also helped that ClickHouse uses a subset of SQL, unlike InfluxDB which uses a superficially SQL-like but practically very different proprietary language.
Every high-volume Influx/Grafana implementation I’ve used has been a disaster. I’m now at a place that uses ClickHouse and I can now see the utility of Grafana
The shape of the data matters. In particular the cardinality of the tags. If clickhouse works well for you, chances are that your use case will be well served by influxdb_iox too
Clickhouse/Druid/Pinot are all columnstores/column-oriented databases. Clickhouse is a relational engine while Druid/Pinot are a different (and older) design using heavy indexing and pre-aggregation. All of them store table data as per-column segments though which is a defining feature leading to high compression and I/O performance.
There's also the badly named wide-column database type like Cassandra, but this is really just advanced or nested key/value rather than what people would consider "columns".
I've found, from personal experience, that it makes a good replacement for time-series databases, even though it's technically not a time-series database. My employer migrated our KPIs and other metrics from InfluxDB to ClickHouse a couple of years ago, and the drastic improvements in performance were well worth the time it took to migrate our data. It also helped that ClickHouse uses a subset of SQL, unlike InfluxDB which uses a superficially SQL-like but practically very different proprietary language.